Empirical model including band-to-band Coulomb interaction for refractive index spectra of quaternary semiconductors

The refractive indices of (Al_0.48In_0.52As)_z(Ga_0.47In_0.53As)_1-z, and Ga_xIn_1-xAs_yP_1-y quaternary materials is presented from a model that takes into account of band-to-band Coulomb interaction and Urbach broadening. We apply an accurate absorption model to calculate the contribution near band-edge region by a complete closed-form Kramers-Kronig transform. A Sellmeier-type single-oscillator model includes all the additional absorption at higher energies.